How difficult is the transition to multi-cellular life?

[stevebowers]

I'm thinking that we could have around 300-500 Earth-like Garden Worlds (even these would only be approximately Earth-like, and most would not support unmodified humans because of biochemical incompatibility);
around 300 ocean worlds with marine fauna (including Europan type worlds and tidally-locked eyeball worlds)
around 300 Titan type worlds with Muuh-like methanogen fauna
around 300 Amunian type worlds with ammonia based biospheres
around 1000 jovian biospheres with macroscopic life, like Ruach
and 1 magnetobiota (the Menexenes). Total: 2400(ish) garden worlds of all kinds. If we keep the 256 figure the total goes down to around 2150 worlds.

Also 158 vitriolic worlds, 356 halogenic worlds, more than 60 seeded Earth-like worlds (in the Garden of Paradise and in the Cybiota realm) and 34 neutron star biospheres, which are relics of artificial ecopoeisis rather than natural abiogenesis. Some of these have seeded nearby systems through panspermia, so they are equal to natural worlds in many ways.

[Evil DoDo]

I'm thinking that we could have around 300-500 Earth-like Garden Worlds (even these would only be approximately Earth-like, and most would not support unmodified humans because of biochemical incompatibility);
around 300 ocean worlds with marine fauna (including Europan type worlds and tidally-locked eyeball worlds)
around 300 Titan type worlds with Muuh-like methanogen fauna
around 300 Amunian type worlds with ammonia based biospheres
around 1000 jovian biospheres with macroscopic life, like Ruach
and 1 magnetobiota (the Menexenes). Total: 2400(ish) garden worlds of all kinds. If we keep the 256 figure the total goes down to around 2150 worlds.

Also 158 vitriolic worlds, 356 halogenic worlds, more than 60 seeded Earth-like worlds (in the Garden of Paradise and in the Cybiota realm) and 34 neutron star biospheres, which are relics of artificial ecopoeisis rather than natural abiogenesis. Some of these have seeded nearby systems through panspermia, so they are equal to natural worlds in many ways.

I think there should be more terrestrial worlds or less jovian worlds, because I do not understand why should there be a thousand of them.

[ProxCenBound]

I'm thinking that we could have around 300-500 Earth-like Garden Worlds (even these would only be approximately Earth-like, and most would not support unmodified humans because of biochemical incompatibility);
around 300 ocean worlds with marine fauna (including Europan type worlds and tidally-locked eyeball worlds)
around 300 Titan type worlds with Muuh-like methanogen fauna
around 300 Amunian type worlds with ammonia based biospheres
around 1000 jovian biospheres with macroscopic life, like Ruach
and 1 magnetobiota (the Menexenes). Total: 2400(ish) garden worlds of all kinds. If we keep the 256 figure the total goes down to around 2150 worlds.

Also 158 vitriolic worlds, 356 halogenic worlds, more than 60 seeded Earth-like worlds (in the Garden of Paradise and in the Cybiota realm) and 34 neutron star biospheres, which are relics of artificial ecopoeisis rather than natural abiogenesis. Some of these have seeded nearby systems through panspermia, so they are equal to natural worlds in many ways.

This sounds mostly good to me, although I would lean towards 500 Earth-ish garden worlds. Also, I concur that 1,000 jovian biospheres seems too high, why it would be the most common place for life to develop? Perhaps 50 or 100 would be better - seems like a difficult place for abiogenesis.

[stevebowers]

I am fairly sure that Jovian worlds are more common than Earth-like worlds. Gas giants and terrestrial worlds appear to be roughly equal in frequency, but only a fraction of terrestrials are Earth-like.

On the other hand, it is entirely possible that there is a special class of gas giant that is more hospitable to life than a typical gas giant, so maybe gas giant biospheres are rarer than I expect. One problem with life in a gas giant is that the environment does not seem to hold many suitable environments for abiogenesis. I've suggested elsewhere that most gas giants are actually seeded by local panspermia, so the incidence of jovian biospheres may be highly dependent on the incidence of life-bearing jovian moons.

[iancampbell]

I think it is also possible that there is a rare class of worlds; ones with two entirely separate and mutually lethal biospheres (because of conditions) on the same world.

How? Consider a Titan-type moon in orbit around a gas giant, with other sizable moons sharing the primary. The surface has Muuh-type life, and a water ocean beneath the crust has the same sort of life (perhaps sulfur-based) as our current thoughts about Europa.

[Avalancheon]

I'm thinking that we could have around 300-500 Earth-like Garden Worlds (even these would only be approximately Earth-like, and most would not support unmodified humans because of biochemical incompatibility);
around 300 ocean worlds with marine fauna (including Europan type worlds and tidally-locked eyeball worlds)
around 300 Titan type worlds with Muuh-like methanogen fauna
around 300 Amunian type worlds with ammonia based biospheres
around 1000 jovian biospheres with macroscopic life, like Ruach
and 1 magnetobiota (the Menexenes). Total: 2400(ish) garden worlds of all kinds. If we keep the 256 figure the total goes down to around 2150 worlds.

Also 158 vitriolic worlds, 356 halogenic worlds, more than 60 seeded Earth-like worlds (in the Garden of Paradise and in the Cybiota realm) and 34 neutron star biospheres, which are relics of artificial ecopoeisis rather than natural abiogenesis. Some of these have seeded nearby systems through panspermia, so they are equal to natural worlds in many ways.

You said that in the Terragen sphere, there are about 2500 distinct biospheres with macroscopic life: And of these life bearing planets, only 1 in 10 would be Earth-like. Shouldn't that number be higher, though? If you define an Earth-like planet as one that can support Type 1 lifeforms, then that means the oceanic worlds should be added to the count. Therefore, 1 in 5 (or 20%) of these biospheres would be Earth-like.

I also agree with EvilDoDo that the number of Earth-like worlds should be higher. Type 1 lifeforms seem like they would have better odds of evolving naturally than the Type 2, Type 3, or Type 4 lifeforms. In my opinion, they should make up something like 30% or even 40% of the total biospheres.

[stevebowers]

Yes; I'm quite happy to add the oceanic worlds to the Type 1 count. Anders Sandberg stated, way back at the start of the project, that Type 1 biochemistries are the most common, and I agree with that (although this may be a humanocentric parochial bias on our part).